<template>
  <div>
    <p>请选择你要购买的书籍</p>
    <ul>
      <li  v-for="(item,index) in arr" :key="index">{{item.name}}
        <button @click="add(index)">买书</button>
      </li>
    </ul>
    <table border="1" width="500" cellspacing="0">
     <thead>
        <tr>
        <th>序号</th>
        <th>书名</th>
        <th>单价</th>
        <th>数量</th>
        <th>合计</th>
      </tr>
     </thead>
     <tbody>
       <tr 
         v-for="(item,index) in arr" :key="index">
         <td>{{index+1}}</td>
         <td>{{item.name}}</td>
         <td>{{item.price}}</td>
         <td>{{item.count}}</td>
         <td>{{item.price*item.count}}</td>
       </tr>
     </tbody>
    </table>
    <p>总价格为:{{total}} </p>
  </div>
</template>

<script>

export default {

  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
    };
  },
  methods: {
    add(i){
      // console.log(index);
      this.arr[i].count++
    }
  },
  computed: {
    total(){
   return this.arr.reduce((sum,obj)=>{
       return sum=sum+obj.price*obj.count
      },0)
    }
  }
};
</script>
<style scoped>
ul{
  text-align: left;
}
</style>